Shuts off while driving

When it doesn't start, the tachometer doesn't move. I don't hear the fuel pump run when I turn on the key. I need to buy the code reader, please give me some days to get it. I'll be back soon.
Many thanks Roy,
Francesco

Hello, here I'm.

I bought an ODB2 codes reader. So the situation is:
a) There are no codes set in PCM, there are no codes in memory. The vehicle's instrument checker (when you turn on the key with both buttons, trip and reset, pushed) still report error 905 and 999.
B) there is no check engine light on.
C) when it doesn't start, the RPM tachometer moves a little while cranking.
D) when it doesn't start, I don't hear the fuel pump.

Also,
e) the instrument cluster and the heater panel have been re-welded.
F) the speed sensor has been disconnected without result
g) the oxygen sensor has been disconnected and it seems get worse; it shuts off after 30/40 meters and it has more difficult to start again.

Oops. Sorry, I forgot to tell. My vehicle has an electronic sequential LPG system mounted on. It starts with LPG in emergency mode, but doesn't start with gasoline.
I'll try the several check listed in the engine stalls articles, meanwhile any idea will be appreciate.
Thanks and have a nice day,
Francesco.

Hello Roy,

Sorry for my late reply. I checked fuel pressure: result zero, no pressure at all. So I checked the fuel pump: fuel pump not working! I tested directly on battery. Nothing. So, I bought a new fuel pump and replaced the old one. Now pressure is okay. The problem has gone. Now my Chrysler runs fine.
Hope this post may help somebody also.
Thanks Roy.